The present invention relates to a method of and apparatus for automatically correcting position of a TV camera which takes the image of an object for measuring desired data concerning the object, through elimination of any deviation of the TV camera position from the correct position. More particularly, the invention is concerned with a method of and apparatus for correcting the position of a TV camera, suitable for use in a system for examining the beam axis alignment of automotive headlamp in an automobile assembly line.
Systems for measuring various data of an object by means of a TV camera have been known, a typical example of which is a system for examining the beam axis alignment of automotive headlamp in an automobile assembly line. In the known system for examining the automotive beam axis alignment, the measurement is made on an assumption that the TV camera for taking up the screen image of the light distribution pattern of the headlamp beam applied to a screen is always positioned correctly relative to the screen.
As a matter of fact, however, the position of the TV camera is often deviated from the correct position due to an inferior environmental condition of the system, e.g., vibration or the like. Such a deviation of the TV camera position causes the following problem. Referring to FIG. 1, if the mounting position of the TV camera 200 is deviated from the correct position, the optical axis of the TV camera 200 is deviated by an angle .theta. from the correct position m1 to a wrong position m2. This deviation causes a measurement error of .DELTA.h on the plane P of screen. This measurement error .DELTA.h is expressed by .DELTA.h=l tan .theta., representing the distance between the TV camera 200 and the screen plane P by l. Thus, measurement error is caused to seriously impair the reliability of the measurement data even by a slight deviation of the TV camera position. To obviate this problem, hitherto, the position of the TV camera relative to the screen is checked periodically. Unfortunately, however, a visual check by the operator's eyes is the only effective measure for checking the TV camera position. The conventional checking method involved also problems concerning the mounting precision.